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  Subjects -> ENGINEERING (Total: 2018 journals)
    - CHEMICAL ENGINEERING (161 journals)
    - CIVIL ENGINEERING (154 journals)
    - ELECTRICAL ENGINEERING (86 journals)
    - ENGINEERING (1135 journals)
    - ENGINEERING MECHANICS AND MATERIALS (307 journals)
    - HYDRAULIC ENGINEERING (48 journals)
    - INDUSTRIAL ENGINEERING (52 journals)
    - MECHANICAL ENGINEERING (75 journals)

CHEMICAL ENGINEERING (161 journals)                  1 2     

ACS Combinatorial Science     Full-text available via subscription   (Followers: 9)
Acta Crystallographica Section B: Structural Science, Crystal Engineering and Materials     Hybrid Journal   (Followers: 4)
Acta Polymerica     Hybrid Journal   (Followers: 6)
Additives for Polymers     Full-text available via subscription   (Followers: 21)
Adhesion Adhesives & Sealants     Hybrid Journal   (Followers: 5)
Advanced Chemical Engineering Research     Open Access   (Followers: 8)
Advanced Powder Technology     Hybrid Journal   (Followers: 12)
Advances in Chemical Engineering     Full-text available via subscription   (Followers: 16)
Advances in Chemical Engineering and Science     Open Access   (Followers: 22)
Advances in Polymer Technology     Hybrid Journal   (Followers: 11)
African Journal of Pure and Applied Chemistry     Open Access   (Followers: 4)
Annual Review of Analytical Chemistry     Full-text available via subscription   (Followers: 9)
Annual Review of Chemical and Biomolecular Engineering     Full-text available via subscription   (Followers: 10)
Anti-Corrosion Methods and Materials     Hybrid Journal   (Followers: 4)
Applied Petrochemical Research     Open Access   (Followers: 3)
Asia-Pacific Journal of Chemical Engineering     Hybrid Journal   (Followers: 6)
Biochemical Engineering Journal     Hybrid Journal   (Followers: 8)
Biomass Conversion and Biorefinery     Partially Free   (Followers: 5)
BMC Chemical Biology     Open Access   (Followers: 4)
Brazilian Journal of Chemical Engineering     Open Access   (Followers: 2)
Bulletin of the Chemical Society of Ethiopia     Open Access   (Followers: 1)
Carbohydrate Polymers     Hybrid Journal   (Followers: 9)
Catalysts     Open Access   (Followers: 7)
Chemical and Engineering News     Free  
Chemical and Materials Engineering     Open Access  
Chemical and Petroleum Engineering     Hybrid Journal   (Followers: 8)
Chemical and Process Engineering     Open Access   (Followers: 3)
Chemical and Process Engineering Research     Open Access   (Followers: 5)
Chemical Communications     Full-text available via subscription   (Followers: 29)
Chemical Engineering & Technology     Hybrid Journal   (Followers: 24)
Chemical Engineering and Processing: Process Intensification     Hybrid Journal   (Followers: 10)
Chemical Engineering and Science     Open Access   (Followers: 2)
Chemical Engineering Communications     Hybrid Journal   (Followers: 10)
Chemical Engineering Journal     Hybrid Journal   (Followers: 20)
Chemical Engineering Research and Design     Hybrid Journal   (Followers: 16)
Chemical Engineering Science     Hybrid Journal   (Followers: 11)
Chemical Geology     Hybrid Journal   (Followers: 9)
Chemical Papers     Hybrid Journal   (Followers: 3)
Chemical Product and Process Modeling     Full-text available via subscription   (Followers: 3)
Chemical Reviews     Full-text available via subscription   (Followers: 325)
Chemical Society Reviews     Full-text available via subscription   (Followers: 31)
Chemical Technology     Open Access   (Followers: 5)
ChemInform     Hybrid Journal   (Followers: 3)
Chemistry & Industry     Hybrid Journal   (Followers: 2)
Chemistry Central Journal     Open Access   (Followers: 5)
Chemistry of Materials     Full-text available via subscription   (Followers: 223)
Chemometrics and Intelligent Laboratory Systems     Hybrid Journal   (Followers: 6)
ChemSusChem     Hybrid Journal   (Followers: 7)
Chinese Chemical Letters     Full-text available via subscription   (Followers: 1)
Chinese Journal of Chemical Engineering     Full-text available via subscription   (Followers: 3)
Coke and Chemistry     Hybrid Journal  
Coloration Technology     Hybrid Journal   (Followers: 1)
Computational Biology and Chemistry     Hybrid Journal   (Followers: 8)
Computer Aided Chemical Engineering     Full-text available via subscription   (Followers: 2)
Computers & Chemical Engineering     Hybrid Journal   (Followers: 7)
CORROSION     Full-text available via subscription  
Corrosion Reviews     Full-text available via subscription   (Followers: 4)
Crystal Research and Technology     Hybrid Journal   (Followers: 2)
Current Opinion in Chemical Engineering     Open Access   (Followers: 3)
Education for Chemical Engineers     Hybrid Journal   (Followers: 4)
Ekologia : The Journal of Institute of Landscape Ecology of Slovak Academy of Sciences     Open Access  
Eksergi     Open Access  
Emerging Trends in Chemical Engineering     Full-text available via subscription  
European Polymer Journal     Hybrid Journal   (Followers: 41)
Fibers and Polymers     Full-text available via subscription   (Followers: 3)
Focusing on Modern Food Industry     Open Access   (Followers: 3)
Frontiers of Chemical Science and Engineering     Hybrid Journal   (Followers: 1)
Geochemistry International     Hybrid Journal  
Handbook of Powder Technology     Full-text available via subscription   (Followers: 2)
High Performance Polymers     Hybrid Journal  
Indian Chemical Engineer     Hybrid Journal   (Followers: 3)
Indian Journal of Chemical Technology (IJCT)     Open Access   (Followers: 12)
Industrial & Engineering Chemistry     Full-text available via subscription   (Followers: 9)
Industrial & Engineering Chemistry Research     Full-text available via subscription   (Followers: 18)
Industrial Chemistry Library     Full-text available via subscription   (Followers: 4)
Info Chimie Magazine     Full-text available via subscription  
International Journal of Chemical and Petroleum Sciences     Open Access   (Followers: 2)
International Journal of Chemical Engineering     Open Access   (Followers: 6)
International Journal of Chemical Reactor Engineering     Full-text available via subscription   (Followers: 3)
International Journal of Chemical Technology     Open Access   (Followers: 4)
International Journal of Chemoinformatics and Chemical Engineering     Full-text available via subscription   (Followers: 2)
International Journal of Food Science     Open Access   (Followers: 2)
International Journal of Industrial Chemistry     Open Access  
International Journal of Polymeric Materials     Hybrid Journal   (Followers: 3)
International Journal of Science and Engineering     Open Access   (Followers: 7)
International Journal of Waste Resources     Open Access   (Followers: 5)
ISRN Chemical Engineering     Open Access   (Followers: 4)
ISRN Polymer Science     Open Access   (Followers: 11)
Journal of Applied Crystallography     Hybrid Journal   (Followers: 4)
Journal of Applied Electrochemistry     Hybrid Journal   (Followers: 11)
Journal of Applied Polymer Science     Hybrid Journal   (Followers: 206)
Journal of Biomaterials Science, Polymer Edition     Hybrid Journal   (Followers: 8)
Journal of Chemical & Engineering Data     Full-text available via subscription   (Followers: 7)
Journal of Chemical Ecology     Hybrid Journal   (Followers: 2)
Journal of Chemical Engineering     Open Access   (Followers: 4)
Journal of Chemical Engineering and Materials Science     Open Access  
Journal of Chemical Science and Technology     Open Access   (Followers: 2)
Journal of Chemical Sciences     Partially Free   (Followers: 15)
Journal of Chemical Technology & Biotechnology     Hybrid Journal   (Followers: 2)
Journal of Chemical Theory and Computation     Full-text available via subscription   (Followers: 9)

        1 2     

Journal Cover Chemical Engineering Science
   [13 followers]  Follow    
   Hybrid Journal Hybrid journal (It can contain Open Access articles)
     ISSN (Print) 0009-2509
     Published by Elsevier Homepage  [2575 journals]   [SJR: 1.033]   [H-I: 103]
  • CFD modeling of the H2/N2 separation with a nickel/α-alumina
           microporous membrane
    • Abstract: Publication date: 17 February 2015
      Source:Chemical Engineering Science, Volume 123
      Author(s): Yacine Benguerba , Jamal Amer , Barbara Ernst
      A theoretical model simulating gas mixture separation using a composite inorganic membrane for high temperatures (T>400°C) is proposed. This model simulates operation of membrane described as three layers: metal, metal-support and support. The intermediate layer is considered to take into account the part of support with a few amounts of metal where the pore diameter is reduced due to the deposited metal on the wall of the pores. The computational fluid dynamics (CFD) approach is used. The simulation is based on the numerical solution of the three-dimensional (3D) Navier–Stokes equations coupled with the species governing equations on the three dimensional domain representing quite closely the selected module geometry. The permeability fluxes are calculated at different temperature and transmembrane pressures and compared with the experimental data. The simulation predictions show fairly good agreement with the measured permeation data.


      PubDate: 2014-12-18T08:41:51Z
       
  • On the single and two-bubble class models for bubble column reactors
    • Abstract: Publication date: 17 February 2015
      Source:Chemical Engineering Science, Volume 123
      Author(s): Xuedong Jiang , Ning Yang , Jiahua Zhu , Bolun Yang
      A number of bubble column reactor models have been developed in literature on the basis of single-bubble class (SBC) or two-bubble class (TBC) concepts. While some researchers claimed that there was no significant difference between the two models, others believed that the TBC model was in better agreement with experimental data. A systematic and comparative analysis is carried out in this study to evaluate the model performance. We find that the dispute is relevant to the different sub-models used in these studies for hydrodynamics, mass transfer, and reaction kinetics as well as gas contraction. There are basically two aspects dominating the model calculation. The first is the hydrodynamic model for gas holdup, and the second is whether the system is limited by reaction or mass transfer. Then a new reactor model is developed to replace the empirical correlations for gas holdup with the dual-bubble-size (DBS) model, and the empirical contraction factor is eliminated by introducing the gas state equation and overall mass balance. The exchange between the small and large bubbles is also taken into account in the species transport equations. The model calculation indicates that the exchange can be neglected for reaction limited systems but becomes important for mass transfer limited systems. The new reactor model is in reasonable agreement with CFD simulation.


      PubDate: 2014-12-18T08:41:51Z
       
  • A multi-scale, mechanistic model of a wet granulation process using a
           novel bi-directional PBM–DEM coupling algorithm
    • Abstract: Publication date: 17 February 2015
      Source:Chemical Engineering Science, Volume 123
      Author(s): Dana Barrasso , Thomas Eppinger , Frances E. Pereira , Ravindra Aglave , Kristian Debus , Sean K. Bermingham , Rohit Ramachandran
      In this study, a novel mechanistic model for a wet granulation process is presented, combining the techniques of population balance modeling and discrete element methods to predict critical quality attributes of the granule product, such as porosity and size distribution. When applied to a twin screw granulation process, the model shows sensitivities to the screw element type and geometry, as well as material properties (binder viscosity, pore saturation) and process parameters (screw speed, liquid-to-solid ratio). Predicted trends are consistent with experimental observations in the literature. Using this modeling framework, a model-based approach can be used to implement Quality by Design, establishing a design space to transition towards a quantitative mechanistic understanding of wet granulation processes.


      PubDate: 2014-12-18T08:41:51Z
       
  • Kinetics of the absorption of carbon dioxide into aqueous hydroxides of
           lithium, sodium and potassium and blends of hydroxides and carbonates
    • Abstract: Publication date: 17 February 2015
      Source:Chemical Engineering Science, Volume 123
      Author(s): Shahla Gondal , Naveed Asif , Hallvard F. Svendsen , Hanna Knuutila
      In the present work the rates of absorption of carbon dioxide into aqueous hydroxides (0.01–2.0kmol.m−3) and blends of hydroxides and carbonates with mixed counter ions (1–3kmol.m−3) containing Li+, Na+ and K+ as cations were studied in a String of Discs Contactor (SDC). The temperature range was 25–64°C and the conditions were such that the reaction of CO2 could be assumed pseudo-first-order. The dependence of the reaction rate constant on temperature and concentration/ionic strength and the effect of counter ions were verified for the reaction of CO2 with hydroxyl ions in these aqueous electrolyte solutions. The infinite dilution second order rate constant k O H − ∞ was derived as an Arrhenius temperature function and the ionic strength dependency of the second order rate constant, k O H − , was validated by the widely used Pohorecki and Moniuk model (Pohorecki and Moniuk, 1988) with refitted parameters. The contribution of ions to the ionic strength and the model itself, was extended to the given concentration and temperature ranges. The model with refitted parameters represents the experimental data with less than 12% AARD.


      PubDate: 2014-12-18T08:41:51Z
       
  • Kinetic modeling of methane dehydroaromatization chemistry on Mo/Zeolite
           catalysts in packed-bed reactors
    • Abstract: Publication date: 17 February 2015
      Source:Chemical Engineering Science, Volume 123
      Author(s): Canan Karakaya , Huayang Zhu , Robert J. Kee
      This paper develops a detailed chemical kinetics reaction mechanism to represent methane dehydroaromatization (MDA) chemistry on bi-functional Mo/zeolite catalysts. The model is validated using a range of previously published results from packed-bed experiments. The reaction mechanism consists of four methane activation reactions on Mo2C sites. The resulting gas-phase hydrogen and ethylene continue to react on Brønsted acid sites within the zeolite structure using 46 reaction steps. In addition to the desired benzene formation, the model also predicts the formation of toluene, naphthalene, and other side products. In addition to reaction kinetics on the catalyst surfaces, the packed-bed model incorporates a Dusty-Gas model that accommodates ordinary and Knudsen diffusion as well as pressure-driven advection. Because the model represents essentially all published reports of MDA performance, it is reasonably expected that the model can be applied as a predictive tool to support reactor and process development.


      PubDate: 2014-12-18T08:41:51Z
       
  • A scheme of correlation for frictional pressure drop in steam–water
           two-phase flow in helicoidal tubes
    • Abstract: Publication date: 17 February 2015
      Source:Chemical Engineering Science, Volume 123
      Author(s): Marco Colombo , Luigi P.M. Colombo , Antonio Cammi , Marco E. Ricotti
      In the nuclear field, helically coiled tube steam generators (SGs) are considered as a primary option for different nuclear reactor projects of Generation III+ and Generation IV. For their characteristics, in particular compactness of the component design, higher heat transfer rates and better capability to accommodate thermal expansion, they are especially attractive for small-medium modular reactors (SMRs) of Generation III+. In this paper, starting from two existing databases, a new correlation is developed for the determination of the two-phase frictional pressure drop. The experimental data cover the ranges 5–65bar for the pressure, 200 to 800kg/m2 s for the mass flux and 0 to 1 for the quality. Two coil diameters have been considered, namely 0.292m and 1.0m. The coil diameter in particular is crucial for a correct estimation of the two-phase frictional pressure drop. Actually, no general correlation reliable in a wide range of coil geometries is available at the moment. Starting from the noteworthy correlation of Lockhart and Martinelli, corrective parameters are included to account for the effect of the centrifugal force, introduced by the helical geometry, and the system pressure. The correlation is developed with the aim to obtain a form of general validity, while keeping as low as possible the number of empirical coefficients involved. The average relative deviation between the correlation and the experimental data is about 12.9% on the whole database, which results the best among numerous literature correlations. In addition, the new correlation is characterized by an extended range of validity, in particular for the diameter of the coil.


      PubDate: 2014-12-18T08:41:51Z
       
  • Cleaning of a model food soil from horizontal plates by a moving vertical
           water jet
    • Abstract: Publication date: 17 February 2015
      Source:Chemical Engineering Science, Volume 123
      Author(s): D.I. Wilson , H. Köhler , L. Cai , J.-P. Majschak , J.F. Davidson
      The removal of layers of a model food soil (dried Xanthan gum containing fluorescent ZnS particles) by a vertical water jet impinging normally on to the plate, generated by a solid stream nozzle which moves across the plate was reported by Köhler et al. (2014). Their experiments investigated nozzle pressures from 0.5 to 2.0barg; nozzle diameters from 0.84–2.66mm, nozzle-layer separation of 20mm, and nozzle traverse speeds of 2.1–126mms−1. The flow parameters and separation are smaller than those typical of industrial jet cleaning operations. The model developed by Wilson et al. (2014) [Chem. Eng. Sci. 109, 183–196] for cleaning of similar layers by a stationary impinging jet was modified to describe the case of moving nozzle. This new model predicted the trends observed in the experiments, and analysis of the data yielded a similar cleaning rate constant to that obtained previously for cleaning of similar layers by stationary jets. The model predicted a non-circular cleaning front which matched that extracted from new experiments in which the flow was interrupted in order to capture this feature. The model allowed the cleaning performance indicators suggested by Köhler et al. (2014) to be expressed quantitatively: these indicated that higher nozzle traverse speeds give increased cleaning time, energy and liquid consumption performance.
      Graphical abstract image

      PubDate: 2014-12-18T08:41:51Z
       
  • Breakthrough performances of metal-exchanged nanotitanate ETS-2 adsorbents
           for room temperature desulfurization
    • Abstract: Publication date: 17 February 2015
      Source:Chemical Engineering Science, Volume 123
      Author(s): Sabereh Rezaei , Maria Ophelia D. Jarligo , Lan Wu , Steven M. Kuznicki
      Engelhard titanosilicate-2 (ETS-2) has shown to be a promising substrate to load active sites for deep H2S removal (to sub-ppm levels) for gas purification applications at room temperature. Because of the high external surface area and the cation exchange capacity of ETS-2, active sites can be highly dispersed and very accessible to H2S molecules making it a novel support material for metal-oxide H2S adsorbents. In this paper, we report the room temperature H2S breakthrough performances of ETS-2 metal exchanged with Ag, Ca, Cu and Zn in comparison to a fully developed commercial H2S adsorbent (R3-11G, 36wt% CuO, BASF). The results indicate the following trend for H2S uptake capacities at room temperature: Cu-ETS-2>Ag-ETS-2>Zn-ETS-2≈R3-11G>Ca-ETS-2≈Na-ETS-2. Cu exchanged ETS-2 displays the highest H2S capacity of 29.7mg H2S/g adsorbent compared to the other investigated materials, making it the most promising metal-exchanged ETS-2 for room temperature desulfurization.


      PubDate: 2014-12-18T08:41:51Z
       
  • Constitutive equation for heat transfer caused by mass transfer
    • Abstract: Publication date: 17 February 2015
      Source:Chemical Engineering Science, Volume 123
      Author(s): Jordan Musser , Madhava Syamlal , Mehrdad Shahnam , David Huckaby
      This paper presents a constitutive equation for the thermal heat transfer associated by mass transfer, applicable to both Eulerian–Eulerian and Eulerian–Lagrangian multiphase computational fluid dynamic models. The proposed equation was incorporated into the open-source multiphase CFD code MFIX (https://mfix.netl.doe.gov) to demonstrate that the numerical predictions match experimental data for the limiting cases of evaporation and condensation. The application of the proposed equation to two cases of a reacting carbon particle yields physically consistent expressions for the heats of reaction.


      PubDate: 2014-12-18T08:41:51Z
       
  • Understanding the capillary behavior using the extended reduced similar
           geometry method
    • Abstract: Publication date: 17 February 2015
      Source:Chemical Engineering Science, Volume 123
      Author(s): Bei Wei , Jian Hou , Kang Zhou , Bo Yu
      Pore scale modeling is used to understand the transport phenomena in porous media. Capillary behavior is an important property in pore scale research. We extend the reduced similar geometry (RSG) method to tangential polygons and simplify the results to concise equations. Based on the RSG method results, the effects of the shape similarity, the shape factor and the contact angle on the capillary behavior are investigated. A new and more accurate parameter is proposed to predict the threshold radius during primary drainage. This parameter is demonstrated to predict the threshold radius accurately for arbitrary polygon shapes and real rock shapes. It also performs better than the traditional predictor when predicting the capillary behavior for concave shapes.
      Graphical abstract image

      PubDate: 2014-12-18T08:41:51Z
       
  • Two-nozzle hydrodynamic focusing
    • Abstract: Publication date: 17 February 2015
      Source:Chemical Engineering Science, Volume 123
      Author(s): Ioannis Psychogios , Dimitrios Hatziavramidis
      Hydrodynamic focusing is a technique used in flow cytometers for sorting and counting cells. This technique may be also applied for sorting and counting cell clusters in other flow devices and has been recently applied to a device of encapsulation of pancreatic cell islets. Existing models of hydrodynamic focusing assume that sample and sheath fluids have identical densities and viscosities even though the sample fluid is loaded with cells. A computational model of hydrodynamic focusing has been developed which allows sample and sheath fluids to have different densities and viscosities and to be miscible or immiscible. Simulations using this model confirm that the most important parameter governing hydrodynamic focusing is the sheath-to-sample-fluid velocity ratio.


      PubDate: 2014-12-18T08:41:51Z
       
  • Characterisation of lactose powder and granules for multivariate wet
           granulation modelling
    • Abstract: Publication date: 17 February 2015
      Source:Chemical Engineering Science, Volume 123
      Author(s): Jan-Georg Rosenboom , Sergiy Antonyuk , Stefan Heinrich , Markus Kraft
      Granulation and size enlargement of particulate materials is a complex process with broad application in industry. For better understanding of the governing mechanisms, we aim to develop a multivariate population balance model to describe granulation. For meaningful model design we require physical characteristics of real materials undergoing granulation. In this work, α-lactose monohydrate powder was investigated as a representative substance due to its broad use in the pharmaceutical industry for tablets. Powder and granules resulting from a high-shear granulation process are characterized with respect to size, shape, porosity and strength using various analytical methods. Particle size distributions are obtained by static image analysis, laser scattering and sieving. Granule porosities are determined using μCT and mercury intrusion porosimetry. Lactose granules show absolute porosities increasing from 30% to 40% along the size classes. The μCT derived visual information of larger granules shows internal pore structures with denser cores and porous shell parts. AFM, SEM and μCT are used for surface characterisation, yielding a maximum value for model particle roughness up to 0.7 μ m . The strength of the product granules measured via uniaxial compression testing follows a logarithmic decrease with size from 1.2 to 0.2MPa. The multivariate data set was then used for model performance analysis and parameter fitting. The size and porosity prediction performance of the computer model could be improved using the newly available data. The rate of coagulation was found to be the most dominant simulation parameter. Comparison with the experiment revealed limitations, for example in PSD shape predictions.
      Graphical abstract image Highlights

      PubDate: 2014-12-18T08:41:51Z
       
  • Design of a true moving bed reactor for the direct synthesis of dimethyl
           carbonate
    • Abstract: Publication date: 17 February 2015
      Source:Chemical Engineering Science, Volume 123
      Author(s): B.A.V. Santos , C.S.M. Pereira , V.M.T.M. Silva , J.M. Loureiro , A.E. Rodrigues
      In the present work is proposed the direct synthesis of dimethyl carbonate (DMC) using a true moving bed reactor (TMBR) to enhance the equilibrium yield. A methodology to design the TMBR is proposed, concerning the maximization of reaction conversion and DMC purity at the outlet stream, and the minimization of the desorbent consumption, together in a single-objective function. The design is supported by numerical simulation, which was based on the experimental data collected from our previous works: mass transfer, adsorption over zeolite 3A, reaction kinetics over cerium oxide, and reaction equilibrium. Besides, the design is also supported by the volume separation method and contour maps of relevant performance variables inside the separation region. In addition, the potentiality and weaknesses of a TMBR process, for the DMC production, are discussed. The TMBR here proposed allows a complete separation between water and DMC in extract and raffinate streams, together with a conversion of carbon dioxide around 6% at 30MPa and 363K.
      Graphical abstract image

      PubDate: 2014-12-18T08:41:51Z
       
  • The role of the solid-solution interface in the dissolution of benzoic
           acid
    • Abstract: Publication date: 17 February 2015
      Source:Chemical Engineering Science, Volume 123
      Author(s): Yang Qiu , Xianwen Li , Gaoming Li , Yaling Zhou , Yishen Qiu
      An experiment using holographic interferometry shows that the evolution of the concentration profile produced by the dissolution of a benzoic acid powder compact cannot be satisfactorily described by the traditional treatments of assuming fast solubility equilibrium at the solid surface or equating dissolution rate with the diffusion flux at the boundary. A physical model was developed which incorporates the solid-solution interface into the kinetic description of the dissolution process. This leads to a boundary condition in which the time-dependence of boundary concentration follows an exponential function. The resulting solution to the diffusion equation shows good agreement with experimental data.


      PubDate: 2014-12-18T08:41:51Z
       
  • Iron oxide redox reaction with oxide ion conducting supports for hydrogen
           production and storage systems
    • Abstract: Publication date: 17 February 2015
      Source:Chemical Engineering Science, Volume 123
      Author(s): Fumihiko Kosaka , Hiroyuki Hatano , Yoshito Oshima , Junichiro Otomo
      Improvement of redox reaction kinetics is important for the application of metal oxide redox reactions in energy conversion systems such as chemical looping systems and hydrogen storage. In this study, we focused on physical properties in supports that can affect the redox reaction kinetics of metal oxides. The redox reaction of iron oxide by hydrogen and water vapor was studied with various support materials, ZrO2, CeO2, yttria-stabilized zirconia (YSZ) and gadolinia-doped ceria (GDC), which have different physical properties such as oxide ion and electronic conductivities. Oxide ion conductors such as YSZ and GDC clearly increased the rate of Fe2O3 reduction (Fe2O3→Fe3O4→FeO→Fe). This result suggests that oxygen vacancies and good oxide ion transport properties in the supports may enhance removal of oxygen from iron oxide. In addition, CeO2 and GDC significantly improved the reduction kinetics in the reduction step from FeO to Fe. Furthermore, it was found that these supports have an effect on the oxidation reaction kinetics of iron by water vapor in comparison with ZrO2; that is, they increase the rate of the steam-iron reaction for hydrogen production. The mechanism of the improvement was discussed in terms of oxide ion and electronic conductivity in the supports and water dissociation on the support surfaces.


      PubDate: 2014-12-18T08:41:51Z
       
  • Microscopic analysis of particle detachment from an obliquely oscillating
           plate
    • Abstract: Publication date: 17 February 2015
      Source:Chemical Engineering Science, Volume 123
      Author(s): Murino Kobayakawa , Seiya Kiriyama , Masatoshi Yasuda , Shuji Matsusaka
      Particle detachment from an obliquely oscillating plate was studied experimentally and theoretically. The plate was placed in a horizontal position, and vibrations were applied in the horizontal and vertical directions by piezoelectric vibrators. The frequency of vibration was constant at 280Hz. The amplitude of vibration increased with time and approached a constant value in each experiment. The movement of micrometer-sized spherical particles was analyzed using images captured by a high-speed microscope camera, which showed that the particles rolled on the plate before detaching from the surface, and that the rolling significantly reduced the adhesive force between the particles and surface. Furthermore, the removal efficiency, defined by the number ratio of detached particles to total particles, was analyzed as a function of the horizontal and vertical vibration accelerations. It was found that the removal efficiency was significantly affected by the horizontal vibration acceleration. These experimental results can be explained by the force and moment balance model.
      Graphical abstract image

      PubDate: 2014-12-18T08:41:51Z
       
  • Role of reactive oxygen species in the dechlorination of trichloroethene
           and 1.1.1-trichloroethane in aqueous phase in UV/TiO2 systems
    • Abstract: Publication date: 17 February 2015
      Source:Chemical Engineering Science, Volume 123
      Author(s): Landry Biyoghe Bi Ndong , Xiaogang Gu , Shuguang Lu , Murielle Primaelle Ibondou , Zhaofu Qiu , Qian Sui , Serge Maurice Mbadinga , Bozhong Mu
      The performance of trichloroethene (TCE) and 1.1.1-trichloroethane (TCA) degradation and dechlorination in aqueous solution using UV and UV/TiO2 was investigated. The effects of pH and the roles of the reactive oxygen species generated during the degradation of the target contaminant were evaluated. The TiO2 was synthesized using a simple hydrothermal solution containing tetrabutyl-titanate and hydrofluoric acid and was characterized by X-ray diffraction (XRD), Brunauer−Emmett−Teller (BET) analysis, transmission electron microscopy (TEM) and X-ray photoelectron spectroscopy (XPS). The results showed that the TiO2, which was in the form of anatase, consisted of well-defined sheet-shaped structures with a rectangular outline≡Ti-F bonds that were formed on the surfaces of photocatalysts. TCE and TCA were completely degraded (100%) in 60 and 90min of illumination, and the degradation of TCE followed the pseudo-first order kinetic model, while the degradation of TCA showed a slow degradation stage initially followed by a fast stage later. The inhibitive effects of pH on TCE degradation were negligible because complete degradation occurred in all the tested pH solutions. Instead, the pH affected the degradation of TCA. Probe compound tests using nitrobenzene (NB) and tetrachloromethane (CT) identified the generation of hydroxyl radicals (•OH) and the superoxide radical anion (O2 •−) in the UV/TiO2 system. Free radical quenching studies demonstrated that all of the studied reactive oxidative species contributed to the TCE and TCA degradation. However, O2 •− and •OH were main detected radicals and contributed more to the degradation process than the 3O2 radical. It is believed that the results from this study can be used to support further UV/TiO2 studies for remediating groundwater contaminated with chlorinated solvents.


      PubDate: 2014-12-18T08:41:51Z
       
  • Flow of pH-responsive microcapsules in porous media
    • Abstract: Publication date: 17 February 2015
      Source:Chemical Engineering Science, Volume 123
      Author(s): Wei Jin Gun , Alexander F. Routh
      This article investigates the use micro-capsules, containing a gelling agent hydroxypropyl cellulose (HPC), to alter flow paths in porous media. The aim is to preferentially block-off high permeability regions, thereby diverting the flow into adjacent un-swept low permeability regions. Micro-capsules with 2–7µm in diameter were made by polymer precipitation through solvent evaporation using poly(4-vinyl pyridine) (PVP) as the shell material. A customised flow tank was constructed to facilitate porous media flow and both single and dual permeability experiments were conducted. Even without gelling agent, the micro-capsules gradually blocked the pore throats of the glass beads network. Following acidification a drop in permeability was observed. This was because swelling of the PVP shell constricted the pore throats. The permeability drop was observed to be more significant for low permeability regions. Flowing micro-capsules through the tank with two permeability regions in parallel allowed the high permeability region to be selectively blocked.
      Graphical abstract image

      PubDate: 2014-12-18T08:41:51Z
       
  • Supercritical water gasification of beet residues: From batch to
           continuous reactor
    • Abstract: Publication date: 17 February 2015
      Source:Chemical Engineering Science, Volume 123
      Author(s): Félicité Ondze , Olivier Boutin , Jean-Christophe Ruiz , Jean-Henry Ferrasse , Frédéric Charton
      A residue obtained after the distillation of agricultural alcohol called beet residues is gasified in supercritical water to form a mixture of fuel gas. A parametric study and thermodynamic calculations are first proposed in batch reactor. The results show a significant effect of temperature on the overall mass yields. Gasification efficiencies range from 0.60 to 0.90gg−1 when temperature increases from 450 to 600°C. The gas low heating value increases under these conditions from 7.4 to 13.2MJkg−1 of initial dry feedstock. After that, a continuous system designed for hydrothermal oxidation processes has been used. For supercritical water gasification, the reduction of total organic carbon in the liquid effluent output presents a little variation, between 59 and 69%, when the operating conditions are changed. To increase the reaction temperature, supercritical water partial oxidation has been conducted. The highest carbon gasification yield is obtained for the highest equivalent molar ratio, indicating a great interest of partial oxidation. Moreover, the results indicate that this process configuration accepts biomass flow variations without influencing the global efficiency.


      PubDate: 2014-12-18T08:41:51Z
       
  • Liquid flow behavior study in SiC foam corrugated sheet using a novel
           ultraviolet fluorescence technique coupled with CFD simulation
    • Abstract: Publication date: 17 February 2015
      Source:Chemical Engineering Science, Volume 123
      Author(s): Hong Li , Fangzhou Wang , Chenchen Wang , Xin Gao , Xingang Li
      The liquid flow behaviors and liquid residence time distribution on different structured SiC foam corrugated sheets are observed experimentally to assess the suitability of the foam structured corrugated packing consisting of SiC foam corrugated sheets. A novel experimental technique using an ultraviolet fluorescence system combined with a HD camera for non-invasive liquid flow behavior measurement has been developed in this article. A model based on computational fluid dynamics (CFD) approach developed in previous work (Li et al., 2011) is used to calculate the liquid flow behaviors and characteristics of residence time for the SiC foam corrugated sheets. Both experimental and numerical results agreed well and demonstrated that the pore size and the extrusion ratio of foam materials played a key role for the liquid flow performance. Finally, the characteristics of flow behaviors obtained from experimental and numerical simulation were compared to the wire mesh sheet. These comparison results showed that SiC-foam sheets have outstanding liquid dispersion capability, which indicates SiC-foam is a promising material for the structured packing.
      Graphical abstract image

      PubDate: 2014-12-18T08:41:51Z
       
  • Optimized H2O2 production in a trickled bed reactor, using water and
           methanol enriched with selectivity promoters
    • Abstract: Publication date: 17 February 2015
      Source:Chemical Engineering Science, Volume 123
      Author(s): Gianluca Gallina , Pierdomenico Biasi , Juan García-Serna , Tapio Salmi , Jyri-Pekka Mikkola
      In the present work a comparison between two different working solutions in the H2O2 catalytic direct synthesis (CDS) was studied in a continuous reactor. The two working solutions (i.e. water and methanol) were chosen due to their large use in the catalytic direct synthesis. Both the working solutions have advantages and drawbacks: it is well known that methanol is mainly used due to the possibility of higher H2 and O2 solubilization compared to water, while water is the “greenest” solvent for excellence. Different parameters such as temperature, gas flow rate and catalyst amount were studied in order to identify the major differences between water and methanol. A study to compare the gases solubility in our conditions in water and methanol was performed in order to understand how gas solubility can affect the reaction. Gas solubility was found to be 10 times higher in methanol compared to water. Consequently the consumption of the reagents was faster in methanol compared to water. Unexpectedly, the final concentration of H2O2 was comparable between water and methanol working solutions at the different operations conditions studied. This indicated that the transport phenomena are important to fine tune the reaction path. The maximum H2O2 was around 2.3wt%.
      Graphical abstract image

      PubDate: 2014-12-18T08:41:51Z
       
  • Immersed boundary method applied to single phase flow past crossing
           cylinders – Heat transfer
    • Abstract: Publication date: 17 February 2015
      Source:Chemical Engineering Science, Volume 123
      Author(s): Q.I.E. Segers , J.A.M. Kuipers , N.G. Deen
      In this work we study heat transfer from a complex geometry consisting of crossing cylinders subject to forced convection. For several sizes of a wire-mesh inserts direct numerical simulations (DNS) are performed using an implicit implementation of the immersed boundary method (IBM). The local heat flux is studied and compared to the total heat flux. A heat transfer correlation is derived describing the Nusselt number as a function of the Reynolds number and the ratio of the pitch to the cylinder diameter, p / D .


      PubDate: 2014-12-18T08:41:51Z
       
  • Predicting kinetic dependences and closing the balance: Wei and Prater
           revisited
    • Abstract: Publication date: 17 February 2015
      Source:Chemical Engineering Science, Volume 123
      Author(s): Denis Constales , Gregory S. Yablonsky , Guy B. Marin
      The chemical system of monomolecular reactions among n species, first analysed in the classical paper by Wei and Prater (1962) was revisited. It was shown that using symmetry relationships, based on all the equilibrium constants and n ( n − 1 ) / 2 known dependences, all remaining kinetic dependences can be calculated. A new method of closing the mass balance for such a complex chemical system was developed, using only measurements of one or a few species, and based on symmetry relations. A new method of testing completeness of a kinetic description was proposed, using the properties of the trace sum of components, i.e., the sum of all concentration dependences, each of which is started from maximal initial concentration.


      PubDate: 2014-12-18T08:41:51Z
       
  • Morphological and electrochemical study of MnxOy nanoparticle layers
           prepared by electrospraying
    • Abstract: Publication date: 17 February 2015
      Source:Chemical Engineering Science, Volume 123
      Author(s): Jiří Maršálek , Josef Chmelař , Jaromír Pocedič , Juraj Kosek
      We are using the electro-hydrodynamic atomization technique (also called electrospraying) for the deposition of fine nanoparticle thin layers of different morphologies. This deposition method has a potential to enable massive fabrication of nanostructured products, but it is necessary to optimize the spraying process to reach the required product qualities. We focus on the preparation of basic (without carbon additives) nanostructured manganese oxide layers deposited on stainless steel substrates. The system of nanostructured MnO2 (with additives) is commonly used as the electrode in energy storage applications (batteries, supercapacitors). The electrochemistry of deposited layers is influenced mainly by MnO2 morphology, which strongly depends on the spraying conditions. Here we carry out the basic study of the nanostructured manganese oxide layer morphology evolution and its electrochemical changes during: (i) the electrospraying deposition period, (ii) the thermal treatment of deposits, and (iii) the electrochemical oxidation. During the electrochemical oxidation the deposited layers change their morphology and structure resulting in fine nanostructured MnO2 in the form of nanorods. This is a desired product for energy storage applications as confirmed by cyclic voltammetry. Morphology and composition analyses were carried out using Raman microscopy, XPS, SEM and AFM. A comprehensive fundamental analysis of the manganese oxide deposition and transformation processes is presented with the emphasis on the evolution of the deposited layer morphology.


      PubDate: 2014-12-18T08:41:51Z
       
  • Mixing of binary fluids with composition-dependent viscosity in a T-shaped
           micro-device
    • Abstract: Publication date: 17 February 2015
      Source:Chemical Engineering Science, Volume 123
      Author(s): Chiara Galletti , Giacomo Arcolini , Elisabetta Brunazzi , Roberto Mauri
      The process of laminar mixing in a T-shaped micro-device is studied by direct numerical simulation for a model binary mixture, composed of two fluids having the same density and the same viscosity, yet presenting a strong fluidity of mixing effect, i.e. the viscosity of the mixture is a function of its composition. In all cases, the inlet streams remain separated up to a critical Reynolds number, corresponding to the transition from a vortex flow regime, with a double mirror symmetry, to an engulfment flow regime, with a point central symmetry. In the case of a positive fluidity of mixing, the onset of the engulfment regime is accompanied by a sharp increase of the degree of mixing, with the critical Re decreasing as the fluidity of mixing increases. On the contrary, when the fluid mixture has a larger viscosity than that of its pure components, a viscous layer forms at the confluence of the inlet flows, which tends to keep the two streams separated. Therefore, in this case, no sudden increase of the degree of mixing is observed at the onset of the engulfment regime.


      PubDate: 2014-12-18T08:41:51Z
       
  • Multi-fluid reactive modeling of fluidized bed pyrolysis process
    • Abstract: Publication date: 17 February 2015
      Source:Chemical Engineering Science, Volume 123
      Author(s): Abhishek Sharma , Shaobin Wang , Vishnu Pareek , Hong Yang , Dongke Zhang
      A multiphase reactive model of biomass pyrolysis process has been implemented by integrating the reaction kinetics of the thermo-chemical decomposition of biomass with the hydrodynamics of the fluidized bed. The model was validated with the experimental data of biomass pyrolysis in the presence of a sand bed. The simulation results were examined to analyze the effect of reactor temperature, superficial gas velocity and biomass particle size on the bed hydrodynamics and product yields. It was found that at temperatures higher than 500°C, there was a significant conversion of primary tar into NCG (non-condensable gases) due to thermal cracking inside the reactor. However, the increase in superficial gas velocity led to higher concentration of tar due to lower residence time for tar cracking reactions. Any increase in biomass particle size reduced the yield of volatile products due to decrease in the rate of heat transfer, which in turn increased the yield of biochar.


      PubDate: 2014-12-18T08:41:51Z
       
  • Influence of jet–jet interaction on droplet size and jet instability
           in immiscible liquid–liquid system
    • Abstract: Publication date: 17 February 2015
      Source:Chemical Engineering Science, Volume 123
      Author(s): Harisinh Parmar , Vishnu Pareek , Chi M. Phan , Geoffrey M. Evans
      This work investigates the effects of multiple jet interactions and single jet instability on jet breakup and droplet size using experimental and computational techniques. In particular, the jet separation distance, jet breakup length and droplet diameter were measured as a function of initial nozzle separation distance and jet volumetric flow rate. It was found that the two jets moved closer to each other to reach an equilibrium separation distance that was approximately 70% of the spacing between the two nozzles. The distance at which the instabilities were first observed on the surface of the jet was also a function of the initial separation distance. However, it was weakly dependent on the jet velocity. The jet breakup length and resultant droplet diameter were both influenced by flow rate and nozzle separation distance. The jet breakup length was found to decrease with reduction in nozzle spacing at the high flow rates. Interestingly, a linear relationship between droplet diameter and breakup length was found that was largely independent of nozzle spacing and consist with conventional Rayleigh jet breakup theory. The implications of the experimental observations on the design of multi-jet systems are discussed. Furthermore, computational fluid dynamics simulations were also used to identify the mechanism and dynamics of jet instability in the single jet systems. The simulation results were analysed to study the effect of instability on various parameters such as jet breakup, droplet formation and size of emulsion droplets. It was found that at higher volumetric flow rates, the droplets size increased during the jet breakup due to an asymmetric instability. The asymmetric instability was caused by the pressure gradient in the continuous phase and was prevented in double jet systems.
      Graphical abstract image

      PubDate: 2014-12-18T08:41:51Z
       
  • Flat sheet membrane contactor (FSMC) for CO2 separation using aqueous
           amine solutions
    • Abstract: Publication date: 17 February 2015
      Source:Chemical Engineering Science, Volume 123
      Author(s): Francis Bougie , Ion Iliuta , Maria C. Iliuta
      A new multi-flat-sheet membrane contactor (FSMC) was developed and used to investigate CO2 removal from CO2/N2 gas mixture using aqueous 2-amino-2-hydroxymethyl-1,3-propanediol (AHPD) solution in the presence and the absence of piperazine (Pz) as activator. The FSMC was operated under various experimental conditions in order to study the effect of liquid flow rate, gas phase composition, CO2 liquid loading and contactor configuration (number of membranes, type of membrane (PTFE, PP and laminated PTFE/PP) and fluid flow orientation (co- and counter-current)). For comparison purpose, MEA aqueous solution (the benchmark amine used in the CO2 capture process) was also tested under the same experimental conditions. The absorption rates through the membranes were found to increase with the increase of liquid flow rate and CO2 concentration in the gas phase and decrease with the raise of CO2 loading. Pz activated AHPD solution showed better performance than single AHPD solution, and similar absorption fluxes were obtained for AHPD+Pz and MEA solutions. As a proportional increase of the absorption rate with the number of membranes was observed, when required, more membranes can be easily added to a contactor module to increase the absorption performance. A two-scale model accounting for CO2 diffusion in the gas-filled membrane pores, CO2 and amines diffusion/reaction in the liquid-filled membrane pores and CO2 and amines diffusion/reaction in the liquid boundary layer was developed to describe the comportment of the multi-flat-sheet membrane contactor.


      PubDate: 2014-12-18T08:41:51Z
       
  • Dynamics of single, non-spherical ellipsoidal particles in a turbulent
           channel flow
    • Abstract: Publication date: 17 February 2015
      Source:Chemical Engineering Science, Volume 123
      Author(s): D.O. Njobuenwu , M. Fairweather
      Using disk, spherical and needle-like particles with equal equivalent volume diameters, the orientational dynamics of non-spherical particles is studied in a turbulent channel flow. An Eulerian–Lagrangian approach based on large eddy simulation with a dynamic sub-grid scale model is used to predict a fully developed gas–solid flow at a shear Reynolds number Re τ =300. Particle shape and orientation are accounted for by the coupling between Newton׳s law of translational motion and Euler׳s law of rotational motion, both in a Lagrangian framework. The particle shapes are simulated using the super-quadrics form, with the dynamically relevant parameters being the particle aspect ratio, equivalent volume diameter and response time. The translational and orientational behaviour of single particles initially released at three different locations in the wall-normal direction are monitored, with analysis showing a clear distinction between the behaviour of the different particle shapes. The results show that turbulent dispersion forces non-spherical particles to have a broad orientation distribution. The orientational states observed include periodic, steady rotation, tumbling, precessing and nutating. Velocity gradient, aspect ratio and particle inertia all have an effect on the alignment of the particle principal axis to the inertial axes. Unlike spherical particles, the disk and needle-like particles display a transition from one orientational state to another, especially when their initial position is in the near-wall region, with the frequency of this transition highest for the disk-like particle. Overall, this study leads to an improved understanding of the significance of shape on particle behaviour which is of relevance to many practical flows.


      PubDate: 2014-12-18T08:41:51Z
       
  • High performance PVDF-TiO2 membranes for water treatment
    • Abstract: Publication date: 17 February 2015
      Source:Chemical Engineering Science, Volume 123
      Author(s): J.-P. Méricq , J. Mendret , S. Brosillon , C. Faur
      In order to obtain low-fouling membranes, TiO2 nanoparticles were entrapped in PVDF membranes prepared by the NIPS wet-process. Typical asymmetric membrane structure was obtained. Membrane structure, hydrophilic properties and permeability were improved in comparison with PVDF neat membrane when increasing TiO2 concentration up to an optimum concentration of 25%wt. Maximum permeate flux of 150L/h/m2 was successfully obtained. For TiO2 content beyond 25%wt, TiO2 particles agglomeration prevents the improvement of hydrophilic properties and permeability. Under UV irradiation, phenomena of super-hydrophilicity due to presence of TiO2 in the composite membrane permits to suppress pure water permeate flux decline and reach higher fluxes. Fouled composite membranes after BSA filtration were successfully cleaned using water and UV irradiation. Permeate flux was totally recovered after this cleaning.


      PubDate: 2014-12-18T08:41:51Z
       
  • A 2.5D computational method to simulate cylindrical fluidized beds
    • Abstract: Publication date: 17 February 2015
      Source:Chemical Engineering Science, Volume 123
      Author(s): Tingwen Li , Sofiane Benyahia , Jean-François Dietiker , Jordan Musser , Xin Sun
      In this paper, the limitations of axisymmetric and Cartesian two-dimensional (2D) simulations of cylindrical gas–solid fluidized beds are discussed. A new method has been proposed to carry out pseudo-two-dimensional (2.5D) simulations of a cylindrical fluidized bed by appropriately combining the benefits of Cartesian 2D and axisymmetric assumptions. This is done by constructing a computational domain consisting of a central thin plate and two wedges. The proposed method was implemented in the open-source code MFIX and applied to the simulation of a lab-scale bubbling fluidized bed with necessary sensitivity study. After a careful grid study to ensure the numerical results are grid independent, detailed comparisons of the flow hydrodynamics were presented against axisymmetric and Cartesian 2D simulations. Furthermore, the 2.5D simulation results have been compared to the three-dimensional (3D) simulation for evaluation. This new approach yields better agreement with the 3D simulation results than with axisymmetric and Cartesian 2D simulations.


      PubDate: 2014-12-18T08:41:51Z
       
  • Solids velocity fields in a cold-flow Gas–Solid Vortex Reactor
    • Abstract: Publication date: 17 February 2015
      Source:Chemical Engineering Science, Volume 123
      Author(s): Jelena Z. Kovacevic , Maria N. Pantzali , Kaustav Niyogi , Niels G. Deen , Geraldine J. Heynderickx , Guy B. Marin
      In a Gas–Solid Vortex Reactor (GSVR), also referred to as a Rotating Fluidized Bed in Static Geometry, a fluidized bed is generated in a centrifugal field by introducing the gas via tangential inlet slots to the reactor chamber. Better heat and mass transfer are observed, making this a promising reactor type for Process Intensification. Developing GSVRs on industrial scale requires, amongst other, a good insight and understanding of the hydrodynamics of the granular flow. In the present work experiments are performed over a wide range of operating conditions in a cold flow pilot-scale set-up. The set-up has a diameter of 0.54m, a length of 0.1m and 36 tangential inlet slots of 2mm. Different materials with solids density between 950–1800kg/m3 and particle diameters of 1–2mm, at varying gas injection velocities from 55 to 110m/s are tested between minimum and maximum solids capacities. All these operating conditions are used to follow the change of granular flow by performing PIV. The rotating fluidized bed can change from a smoothly rotating, densely fluidized bed to a highly bubbling rotating fluidized bed depending on the operating conditions. Bubbling diminishes with increasing solids density and particle diameter. Experimental measurements of azimuthal particle velocity fields in a GSVR are for the first time reported. Azimuthal solids velocity is found to decrease with higher solids density and larger particle diameter. The critical minimum fluidization velocity, that is the minimum velocity at which the complete bed is fluidized, is calculated and the centrifugal bed behavior is mapped in terms of a dimensionless radial gas velocity and a dimensionless particle diameter, as conventionally done for gravitational beds.
      Graphical abstract image

      PubDate: 2014-12-18T08:41:51Z
       
  • Nonlinear control of continuous cultures of Porphyridium purpureum in a
           photobioreactor
    • Abstract: Publication date: 17 February 2015
      Source:Chemical Engineering Science, Volume 123
      Author(s): Sihem Tebbani , Filipa Lopes , Giuliana Becerra Celis
      Advanced control strategies proved to be promising tools to improve the performances of microalgae production systems, especially in the perspective of large scale cultivation plants. This paper proposes the validation of a nonlinear control strategy with experimental results. Additionally, the on-line estimation of the biomass concentration in a photobioreactor is presented. The proposed control law maintains the biomass concentration at a targeted level. This is achieved by a state feedback linearizing control law in an inner loop, in addition to a Proportional Integral regulator with an anti-windup compensation in an outer loop. To cope with the lack of on-line biomass concentration measurements, this variable is estimated on-line by an Extended Kalman Filter, based on available on-line measurements (pH, incident light intensity and dissolved carbon dioxide concentration). Performance and robustness of the proposed control strategy are assessed through experimental results obtained with cultures of the microalgae Porphyridium purpureum in a laboratory-scale continuous photobioreactor.


      PubDate: 2014-12-18T08:41:51Z
       
  • Numerical evaluation of stresses acting on particles in high-pressure
           microsystems using a Reynolds stress model
    • Abstract: Publication date: 17 February 2015
      Source:Chemical Engineering Science, Volume 123
      Author(s): S. Beinert , T. Gothsch , A. Kwade
      In the present study a model was developed which enables to calculate the stress acting on particles induced by the fluid flow in microchannels. Computational fluid dynamics (CFD) was used to simulate the flow field in five different microchannel geometries. With the help of a Reynolds-stress model and a stationary particle tracking a quantification of stresses in different geometries at varying pressure differences is possible. Furthermore, the effect of cavitation which occurs if the fluid expands to ambient pressure was investigated. The mass flow rates determined by the simulations are in good agreement with the ones determined experimentally. Except for the z-channel the computed stresses are in good agreement with previously conducted dispersion experiments. Additionally, the computed fluid stress was compared with the calculated Kolmogorov length scale to validate the results.


      PubDate: 2014-12-18T08:41:51Z
       
  • Bayesian inference of chemical kinetic models from proposed reactions
    • Abstract: Publication date: 17 February 2015
      Source:Chemical Engineering Science, Volume 123
      Author(s): Nikhil Galagali , Youssef M. Marzouk
      Bayesian inference provides a natural framework for combining experimental data with prior knowledge to develop chemical kinetic models and quantify the associated uncertainties, not only in parameter values but also in model structure. Most existing applications of Bayesian model selection methods to chemical kinetics have been limited to comparisons among a small set of models, however. The significant computational cost of evaluating posterior model probabilities renders traditional Bayesian methods infeasible when the model space becomes large. We present a new framework for tractable Bayesian model inference and uncertainty quantification using a large number of systematically generated model hypotheses. The approach involves imposing point-mass mixture priors over rate constants and exploring the resulting posterior distribution using an adaptive Markov chain Monte Carlo method. The posterior samples are used to identify plausible models, to quantify rate constant uncertainties, and to extract key diagnostic information about model structure—such as the reactions and operating pathways most strongly supported by the data. We provide numerical demonstrations of the proposed framework by inferring kinetic models for catalytic steam and dry reforming of methane using available experimental data.


      PubDate: 2014-12-18T08:41:51Z
       
  • Base promoted hydrogenolysis of lignin model compounds and organosolv
           lignin over metal catalysts in water
    • Abstract: Publication date: 17 February 2015
      Source:Chemical Engineering Science, Volume 123
      Author(s): Hannelore Konnerth , Jiaguang Zhang , Ding Ma , Martin H.G. Prechtl , Ning Yan
      Herein we present a systematic investigation on the promotional effect of base in metal catalysed hydrogenolysis of lignin model compounds and organosolv lignin. The research started with the evaluation of pH effects (pH 1–14) on the hydrogenolysis of a lignin β-O-4 model compound over a Ru catalyst (a stable catalyst over a wide pH range), from which a significantly increased selectivity towards monomeric compounds was observed in the presence of base. This promotional effect was studied in detail over bimetallic Ni7Au3 nanoparticles. Addition of a strong base such as NaOH significantly enhanced the activity and selectivity for C-O bond hydrogenolysis over undesired hydrogenation reactions, not only in lignin model compounds but also in real lignin conversion. Notably, the yield for monomeric aromatic compounds from lignin over Ni7Au3 catalyst increased ca. 100% after adding NaOH as a promoter, under the same reaction conditions. Mechanistic study suggest that addition of base significantly reduced the benzene ring hydrogenation activity of the metal catalysts. The effect of adding different bases over various metal catalysts were also investigated.
      Graphical abstract image

      PubDate: 2014-12-18T08:41:51Z
       
  • A drag force correlation for approximately cubic particles constructed
           from identical spheres
    • Abstract: Publication date: 17 February 2015
      Source:Chemical Engineering Science, Volume 123
      Author(s): Y. Chen , J.R. Third , C.R. Müller
      The lattice Boltzmann method has been used to compute the drag force acting on assemblies of approximately cubic particles constructed from eight spheres for a wide range of Reynolds numbers. Based on the simulation data we propose a new drag force correlation for assemblies of approximately cubic particles. We have compared the drag force obtained with that predicted by the correlation proposed by Beetstra et al. (2007), originally proposed for spheres, by considering either the drag acting on individual spheres or the drag acting on an approximately cubic particle composed of eight spheres. The comparisons showed that Beetstra׳s correlation cannot predict the system well. The correlation proposed in this paper enables Euler–Euler and Euler–Lagrangian simulations of approximately cubic particles, allowing the influence of the solid volume fraction in these models to be assessed.
      Graphical abstract image Highlights

      PubDate: 2014-12-18T08:41:51Z
       
  • Gas-liquid flow and mass transfer in a microchannel under elevated
           pressures
    • Abstract: Publication date: 17 February 2015
      Source:Chemical Engineering Science, Volume 123
      Author(s): Chaoqun Yao , Zhengya Dong , Yuchao Zhao , Guangwen Chen
      Flow and mass transfer of gas-liquid slug flow under elevated pressures up to 3.0MPa in a microchannel are investigated with CO2-water system. The results show that the ratio of the initial bubble length to the unit cell length is linear with the injection gas volume fraction under each pressure condition, but the slope decreases with an increase in the system pressure. The mass transfer coefficients are calculated with a unit cell model based on the dissolution rate of gas bubbles. Increasing pressure leads to larger mass transfer coefficients, as well as higher amount of gas absorption during the bubble formation. But the fraction of gas absorption during the bubble formation stage is only about 1.5~4.0% of feeding gas. For the bubble dissolution in the main channel, the dissolution rates at different flow rates differ very little for short contact distances from the T-junction, whereas the balance limitation of dissolution at large contact distances only depends on the amount of liquid in a unit cell.


      PubDate: 2014-12-18T08:41:51Z
       
  • Self-active and recursively selective Gaussian process models for
           nonlinear distributed parameter systems
    • Abstract: Publication date: 17 February 2015
      Source:Chemical Engineering Science, Volume 123
      Author(s): Pei Sun , Junghui Chen , Lei Xie
      Modeling a nonlinear distributed parameter system (DPS) is difficult because it is usually hard to obtain the first-principle models in DPS with strong spatiotemporal characteristics. In this paper, a novel data-driven model, called KL–GP, is proposed based on Karhunen–Loève (KL) decomposition and Gaussian process (GP) models. First, KL decomposition is employed for the time/space separation and dimension reduction. The spatiotemporal output is projected onto a low-dimensional KL space. Subsequently, GP models are used to build the temporal system relationships. Thus, the nonlinear spatiotemporal dynamics can be reconstructed after the time/space synthesis. The advantage of the proposed model is that KL–GP provides the predictive distribution of the outputs and the estimate of the variance of its predicted outputs. The “active data” in the DPS region can be found for model improvement according to the predicted variances. Then the developed self-active KL–GP model is extended to include adaptation and on-line implementation in real time. Systematic design procedures are needed so that the DPS modeling problems can be solved because there are no guidelines to define the architecture needed for evolution in the traditional method. This is particularly good when reducing the computational demand of the DPS model. Simulation results of DPS are presented to demonstrate the effectiveness of the self-active KL–GP modeling method and the recursively selective KL–GP modeling method.


      PubDate: 2014-12-18T08:41:51Z
       
  • Modeling non-Newtonian slurry flow in a flat channel with permeable walls
    • Abstract: Publication date: 17 February 2015
      Source:Chemical Engineering Science, Volume 123
      Author(s): Dmitry Eskin
      A model describing a shear-thinning slurry flow in a flat channel is developed. A diffusive flux modeling approach, which allows calculating particle migration to the channel center, is employed. The model developed accounts also for a fluid leak-off through permeable channel walls. Most of the calculation examples are presented for power-law slurry rheology and a few for Herschel–Bulkley slurries. An evolution of the cross-sectional solids concentration distribution along the channel is analyzed in dependence on slurry system parameters. The computations also revealed a significant effect of particle migration to the channel center on the pressure gradient. The results obtained demonstrate that the particle migration may be important for modeling particle transport in narrow flat channels and, therefore, this phenomenon must be taken into account in the modeling of technological processes, such as proppant transport in hydraulic fracturing.


      PubDate: 2014-12-18T08:41:51Z
       
  • CFD simulations of the effects of small dispersed bubbles on the rising of
           a single large bubble in 2D vertical channels
    • Abstract: Publication date: 17 February 2015
      Source:Chemical Engineering Science, Volume 123
      Author(s): Jinsong Hua
      A computational fluid dynamics based numerical model framework was proposed to simulate two-phase flows with interfacial structures of multiple length-scales, e.g. one large bubble and many small dispersed bubbles. In this numerical method, the large bubble is tracked using a volume of fluid (VOF) method, and the small bubbles are tracked using a discrete particle method (DPM). The couplings among the continuous liquid/gas phases and the discrete small bubble phases are accounted for. To evaluate the model performance, this model was applied to simulate the interaction between a large bubble and many suspended small bubbles in 2D vertical channels under different bubble shape regimes. It is found that the small dispersed bubbles may impose important effects on the rising behavior of the large bubble. The simulations have revealed both hindrance and acceleration effects of small bubbles on the rising of large bubble, which agrees with experimental observations qualitatively.


      PubDate: 2014-12-18T08:41:51Z
       
  • Numerical analysis of strain rate sensitivity in ball indentation on
           cohesive powder Beds
    • Abstract: Publication date: 17 February 2015
      Source:Chemical Engineering Science, Volume 123
      Author(s): M. Pasha , C. Hare , A. Hassanpour , M. Ghadiri
      In the shear deformation of powder beds beyond the quasi-static regime the shear stress is dependent on the strain rate. Extensive work has been reported on the rapid chute flow of large granules but the intermediate regime has not been widely addressed particularly in the case of cohesive powders. However in industrial powder processes the powder flow is often in the intermediate regime. In the present work an attempt is made to investigate the sensitivity of the stresses in an assembly of cohesive spherical particles to the strain rate in ball indentation using the Distinct Element Method. This technique has recently been proposed as a quick and easy way to assess the flowability of cohesive powders. It is shown that the hardness, deviatoric and hydrostatic stresses within a bed, subjected to ball indentation on its free surface, are dependent on the indentation strain rate. These stresses are almost constant up to a dimensionless strain rate of unity, consistent with trends from traditional methods of shear cell testing, though fluctuations begin to increase from a dimensionless strain rate of 0.5. For dimensionless strain rates greater than unity, these stresses increase, with the increase in hardness being the most substantial. These trends correlate well with those established in the literature for the Couette device. However the quantitative value of the strain rate boundary of the regimes differs, due to differences in the geometry of shear deformation bands. Nevertheless, this shows the capability of the indentation technique in capturing the dynamics of cohesive powder flow.
      Graphical abstract image

      PubDate: 2014-12-18T08:41:51Z
       
  • Numerical simulation of the flue gas side of refining vacuum furnace using
           CFD
    • Abstract: Publication date: 17 February 2015
      Source:Chemical Engineering Science, Volume 123
      Author(s): Xuegang Li , Luhong Zhang , Yongli Sun , Bin Jiang , Xingang Li , Jun Wang
      In this work, we aimed to predict the flue gas side performance of a refining vacuum furnace with floor gas burners. The computational fluid dynamics (CFD) approach was employed to simulate the flow, combustion, heat transfer and NO emission. Detailed insights into the flue gas velocity, temperature field and NO mass concentration distribution were obtained with the aid of velocity vectors and contour snapshots. The standard k-ε model was applied to turbulence simulation. The non-premixed turbulent flames and NO emission were predicted using the Laminar Flamelet model. The discrete transfer model (DTM) was applied to the radiative heat transfer simulation. Comparative simulation cases were carried out to investigate the effect of excess air amount on the flue gas temperature distribution and NO emission. Calculations were performed using the commercial packages ANSYS CFX 14.0.


      PubDate: 2014-12-18T08:41:51Z
       
  • Heat integration and optimization of hydrogen production for a 1kW
           low-temperature proton exchange membrane fuel cell
    • Abstract: Publication date: 17 February 2015
      Source:Chemical Engineering Science, Volume 123
      Author(s): Jiao Lei , Hairong Yue , Hao Tang , Bin Liang
      Heat integration and process optimization for the hydrogen production units of 1kW low-temperature proton exchange membrane fuel cells (LT-PEMFCs) were studied. Hydrogen is produced from methane in a process consisting of a steam methane reforming reaction (SMR), a high-temperature water–gas shift reaction (HWGS), a low-temperature water–gas shift reaction (LWGS), and a preferential oxidation reaction (PROX). Using commercial Aspen Plus ® software, the process was designed and simulated with the objective of energy recovery. Furthermore, the unit operation parameters were discussed based on the mass/heat balances. Pinch analysis was applied for heat integration and process optimization to improve the energy recovery level of the hydrogen production system. By integrating system heating, a maximum energy recovery network (MER) and also a relaxed network were developed. The efficiencies of the hydrogen production systems designed with these MER and relaxed networks were 84.3% and 80.1%, respectively. Compared with the MER design, the relaxed network greatly simplifies the hydrogen production process and reduces the exchanger number from 18 to 9. The penalty in terms of power for relaxation is 120W. Sensitivity analysis shows that heat loss and the steam-to-carbon (S/C) ratio are the primary factors influencing the system efficiency, i.e., a 5% heat loss may result in a 7% efficiency drop, and increasing the S/C ratio from 2.5 to 3.0 may result in a 2.5% efficiency drop. The conversion of methane ( X CH 4 ) and the relative deviation from chemical equilibrium for the WGS reactions (both HWGS and LWGS) are secondary factors: efficiency drops 3.5% at X CH 4 =0.8 and at 0.9 of the WGS equilibrium, compared with equilibrium conditions. Finally, the minimum pinch temperature difference (ΔT min) and reaction temperatures have little impact on system efficiency. Therefore, the device insulation and catalyst performance are very important for system performance.


      PubDate: 2014-12-18T08:41:51Z
       
  • Mass transfer and kinetics of carbon dioxide absorption into loaded
           aqueous monoethanolamine solutions
    • Abstract: Publication date: 17 February 2015
      Source:Chemical Engineering Science, Volume 123
      Author(s): Xiao Luo , Ardi Hartono , Saddam Hussain , Hallvard F. Svendsen
      The kinetics of the reaction between carbon dioxide and aqueous solutions of 1 and 5molL−1 monoethanolamine (MEA) pre-loaded with CO2 were investigated over the temperature range 298 to 343K and for CO2 loadings from 0 to 0.4mol CO2/mol MEA in a wetted wall column reactor (WWC) and a string of discs contactor (SDC). A total of 227 new data points are provided for loaded solutions including all underlying data necessary for other researchers to develop own models. Comparisons are made between recent literature data and this study and they are found to be consistent with each other. Three different kinetic models, a simplified soft model, a concentration-based model and an activity-based model were developed and validated against the experimental data and by a penetration type mass transfer model in order to analyze the absorption rate and understand the reaction process. Results show good agreement between the models at low loadings and kinetic parameters are provided for all models. Above a loading of 0.3mol CO2/mol MEA it is recommended to use the activity based model as systematic deviations occurred in the soft and concentration based models. The effect of depletion of free amine at the gas–liquid interface on the kinetic and mass transfer calculations was investigated and it was found insignificant at high amine concentrations, low CO2 loadings, low CO2 driving forces and temperatures. However, the effect does become significant when either reducing the amine concentration or increasing the CO2 driving force, CO2 loading or temperature. Furthermore, there is an upper limit for the CO2 driving force for each amine concentration below which the chemical reaction can be assumed to be in the pseudo 1st order regime.


      PubDate: 2014-12-18T08:41:51Z
       
  • Enhancement effect of lithium-doping functionalization on methanol
           adsorption in copper-based metal-organic framework
    • Abstract: Publication date: 17 February 2015
      Source:Chemical Engineering Science, Volume 123
      Author(s): Ying Wu , Defei Liu , Huiyong Chen , Yu Qian , Hongxia Xi , Qibin Xia
      Grand canonical Monte Carlo (GCMC) simulations combined with density functional theory (DFT) calculations were performed to evaluate the functionality effect of Li-doping on methanol adsorption over copper-based metal–organic frameworks (MOFs). In this work, a new Li-doping structure, Cu-BTC-Li, was theoretically constructed by introducing Li above both sides of organic linkers in Cu-BTC. Compared to the original Cu-BTC, Cu-BTC-Li shows higher methanol capacity and more continuous adsorption behavior in the measured pressure range. It can be attributed to the new adsorption sites (Li-sites) created by Li atoms, which turn to be the first preferential adsorption sites instead of Cu-sites, as revealed by the more exothermic binding energies (BEs) on Li-site (−90.55kJ/mol) than the latter (−45.14kJ/mol). Li-doping also shows varied effects on methanol adsorption at different pressures. The electrostatic interaction between methanol and framework plays a predominant role (with contribution over 95%) in the adsorption at low pressures, and Li-doping enhances adsorption by increasing the electrostatic potential of the framework. Although the dispersive interactions govern the adsorption at high pressures, Li-doping contributes to the dispersion. The present Li-doped functionalization can be extended to design new MOFs with high performance of alcohol capture in the future.
      Graphical abstract image

      PubDate: 2014-12-18T08:41:51Z
       
  • Simultaneous measurements of particle charge density and bubble properties
           in gas-solid fluidized beds by dual-tip electrostatic probes
    • Abstract: Publication date: 17 February 2015
      Source:Chemical Engineering Science, Volume 123
      Author(s): Chuan He , Xiaotao T. Bi , John R. Grace
      The aim of this work was to develop a new dual-tip electrostatic probe for in-situ measurements of particle charge density and bubble properties in bubbling fluidized beds. Probes containing two retractable, vertically-aligned tips were tested in a lab-scale two-dimensional fluidized bed operated in both single bubble injection and freely bubbling modes, with glass beads and polyethylene particles of narrow size distributions as bed materials. Different decoupling methods were proposed and employed to analyze the electrostatic signals from the probes. The estimated particle charge density and bubble rise velocity were found to follow the same trends as those measured by a Faraday cup sampling system and obtained from video images respectively, with relative errors depending on the decoupling methods and probe configurations, especially for polyethylene particles.


      PubDate: 2014-12-18T08:41:51Z
       
  • High-fidelity simulation of the 3-D full-loop gas–solid flow
           characteristics in the circulating fluidized bed
    • Abstract: Publication date: 17 February 2015
      Source:Chemical Engineering Science, Volume 123
      Author(s): Kun Luo , Fan Wu , Shiliang Yang , Mingming Fang , Jianren Fan
      The full-loop gas–solid motions in a three-dimensional circulating fluidized bed are numerically modeled using the computational fluid dynamics combined with the discrete element method. The time-averaged flow characteristics and the particle-scale details related to solid motion are discussed. The results show that solid motion shows an ‘S’ rising path in the riser but a spirally falling behavior in the cyclone. Typical core-annulus flow structure and non-uniform distribution of solid holdup appear in the riser. The inside and outside swirling flows of gas motion as well as the fishtailing phenomenon are captured in the cyclone. The solid residence time in the riser shows an early-occurred peak with a long tail. In the riser, details related to solid motion at the particle-scale level are obtained. The sudden changes of these particle-scale details when increasing the superficial velocity may be considered to be a new criterion of identifying the flow regime change.
      Graphical abstract image

      PubDate: 2014-12-18T08:41:51Z
       
  • Modelling pyrolysis of charring materials: determining flame heat flux
           using bench-scale experiments of medium density fibreboard (MDF)
    • Abstract: Publication date: 17 February 2015
      Source:Chemical Engineering Science, Volume 123
      Author(s): Kaiyuan Li , Dennis S.W. Pau , Jinhui Wang , Jie Ji
      Medium density fibreboard is a homogenous wood product which is a suitable candidate for validating the pyrolysis model of charring materials. For comparison between model and experiment, this article presents the burning behaviour of MDF under cone calorimeter with different experimental conditions. The total incident heat flux, as a significant boundary condition for pyrolysis modelling, is specifically studied both experimentally and theoretically. The experimental conditions were found to have no significant impact on the ignition phase however the sample thickness would lead to different burning behaviours. The total incident heat flux led by cone and flame at sample surface was experimentally measured and the experimental results were evaluated using non-flaming experiments with inert gas. An analytical model based on classical ignition theory is developed to address the mechanism of mass loss caused by incident heat flux, involving the effects of char layer and back boundary. The model shows that the mass loss rate correlates linearly with the total incident heat flux for a specific char layer thickness and back boundary condition. The model was validated for the non-flaming and flaming experiments to further justify the reliability of heat flux measurements. An empirical equation describing the flame heat flux is proposed.


      PubDate: 2014-12-18T08:41:51Z
       
  • Effects of superficial gas velocity and temperature on entrainment and
           electrostatics in gas–solid fluidized beds
    • Abstract: Publication date: 17 February 2015
      Source:Chemical Engineering Science, Volume 123
      Author(s): Turki A. Alsmari , John R. Grace , Xiaotao T. Bi
      The effects of superficial gas velocity and temperature on particle entrainment and electrostatic charges in fluidized binary mixtures of glass beads were investigated in a column of 150mm inner diameter and 2m height. The degree of electrification in the bed was measured by four collision ball probes at different levels. The charge density of entrained particles in the freeboard was determined by a freeboard sampler constructed as a Faraday cup. An instrumented pipe coated with Ni in the reactor exit line measured the electrical current transferred from entrained fine particles by collisions. The particle entrainment flux and electrostatic charge inside the bed and freeboard region increased with increasing superficial gas velocity. Temperature had negligible effect on the entrainment flux over the limited range studied. However, electrostatic charges decreased and the charge polarity reversed as the bed temperature increased from 20 to 75°C.


      PubDate: 2014-12-18T08:41:51Z
       
 
 
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